Efficacy and safety of continued zoledronic acid every 4 weeks versus every 12 weeks in women with bone metastases from breast cancer Results of the OPTIMIZE-2 trial

SUMMARY: Bone is the most common site of metastatic disease, in patients with Breast Cancer. Bisphosphonates inhibit osteoclast-mediated bone resorption and both oral and IV bisphosphonates reduce the risk of developing Skeletal Related Events (SRE’s) and delay the time to SRE’s in patients with Breast Cancer with bone metastases. Bisphosphonates can also reduce bone pain and may improve Quality of life. Of the four bisphosphonates proven to be effective in patients with Breast Cancer with bone metastases, only intravenous Pamidronate (AREDIA®) and Zoledronic acid (ZOMETA®) have been approved in the USA, whereas intravenous and oral Ibandronate and oral Clodronate have been approved in Europe. Both AREDIA® and ZOMETA® are administered every 3 to 4 weeks during the first year, following diagnoses of bone metastases. However, the optimal treatment schedule following this initial phase of treatment has remained unclear. Further, renal toxicity, long bone fractures and OsteoNecrosis of the Jaw (ONJ) have been identified as potential problems with bisphosphonate use. OPTIMIZE-2 is a prospective, randomized, double-blind, multicenter trial, in which the authors evaluated the outcomes of a less intense schedule of ZOMETA® administered every 12 weeks, following one year of the standard initial phase of treatment with bisphosphonates. This study included 403 women with bone metastases from Breast Cancer, who had received 9 or more doses of either intravenous ZOMETA® or AREDIA®, during the first 10-15 months of therapy. The median age was 59 years and patients were randomized (1:1) to receive either ZOMETA® 4 mg IV every 4 weeks (N=200) or every 12 weeks (N=203), for one year. The primary endpoint was Skeletal Related Event (SRE) rate, defined as the proportion of patients with one or more SRE’s (pathologic fractures, spinal cord compression, need for radiotherapy or surgical stabilization of the bone). The primary analysis was non-inferiority, for the difference in SRE rates between the treatment groups. Secondary endpoints included time to first SRE, Skeletal Morbidity Rate (SMR), bone pain score, change in bone turnover markers, and safety. After a median follow up of 11.9 months, the SRE rate was 22% and 23.2% in the ZOMETA® every 4 weeks group and ZOMETA® every 12 weeks group respectively (P=0.724), suggesting that ZOMETA® given every 12 weeks was non-inferior to the q 4 week regimen. The secondary endpoints were comparable as well. More patients had renal toxicities in the ZOMETA® q 4 week group vs q 12 week group (9.6% vs 7.9%, respectively) and two cases (1.0%) of OsteoNecrosis of the Jaw (ONJ) were reported in the ZOMETA® q 4 week group. The authors concluded that the efficacy of continuing ZOMETA® for an additional year at the q 12 week schedule was non-inferior to ZOMETA® given q 4 weeks, among patients who had initially received IV bisphosphonates monthly, for one year or longer. Further the less frequent dosing of ZOMETA® compared with the standard monthly dosing, may be more convenient for the patients and result in less toxicities. Hortobagyi GN, Lipton A, Chew HK, et al. J Clin Oncol 32:5s, 2014 (suppl; abstr LBA9500)